People want to be able to inline-quote via e-mail, with a similar end result as via the web interface (highlight, click “quote”). It’s really unlikely we’d be able to get the results quite the same (extracting the [quote] metadata would be fiendishly tricky), but we could at least recognise common HTML quoting styles, and transmogrify them into the equivalent of how > gets handled in markdown:
Why is recognizing quoted text important?